Coated abrasive



Ma 2, 1939. J. F. A. DAVIS 2,156,492

COATED ABRAS IVE Filed Nov. 8, 1937 I INVENTOR.

Patented May 2, 1939 UNITED STATES PATENT OFFICE 2,156,492 COATED ABRASIVE John F. A. Davis, Hamilton, Mass.

Application November 8, 1937, Serial No. 173,443

3 Claims. (01. 51-185) The invention relates to an improvement in coated abrasives and especially that type of coated abrasive which is subjected to hard distortive usage as in the making of abrasive disks.

Manufacturers of coated abrasives have for many years used, among others, a backing (to which is bonded the abrasive) known in the trade as combination. This backing consists of a layer of fabric glued to a layer of firm nonstretching material such as paper. For many years such backing was also spoken of as cloth-paper because it was usually made of a light-weight cotton cloth glued to a heavy-weight paper, but it has also been best known and sold as combination because of the fact that it was usually a combination of the two most used forms of backing on which abrasives are coated.

Combination has certain definite characteristics. These characteristics are chiefly the ability of the cloth or other fabric element to provide a superior anchorage for abrasive grain and the ability of the paper or other firm fibrous material to resist stretch and distortion. It is a well known fact that properly prepared cotton cloth will hold an abrasive coating by means of a glue-bond far better than will paper. It is also well known that, when so coated, cotton cloth will, by deliberate flexing or through stresses engendered in its use as an abrasive, become flexible or pliable so that it lacks the'firmness and resiliency to withstand stretch or distortion. Paper, on the other hand, does not form as good an anchorage for acoating of abrasive grain but it does withstand stretch and distortion. By gluing a sheet of prepared cotton cloth to a sheet of paper (a process known as combining) a backing is obtained which offers the superior anchorage of the cotton cloth for the coating of abrasive grains and 'theability of the paper to withstand stretch anddistortion.

Combination has provided a superior backing for use of coated abrasives on several types of abrading, sanding, buffing, and grinding machines. It has been developed and used from a lightweight backing (cotton sheeting combined with light paper) to heavy-weight backing (cotton drills combined with heavy paper) with all manner of variations depending on which of the chief characteristics it was desired to emphasize and what weight or bulk was required. For cotton cloths have been substituted from time to time other fabrics, such as linen; and for paper have been substituted other materials possessing its desired characteristics in greater or lesser degree, such as vulcanized fibre.

While various kinds of paper have been used in making combination no paper so used in so far as I know has been especially treated to develop to a higher degree its inherent characteristics of strength, firmness, cohesion, resiliency, and ability to resist stretch and distortion; and also to increase its aflinity or fitness for receiving the bond by which the cloth or fabric is bonded to it.

The individual fibres themselves in paper adaptable to be used in a combination coated abrasive possess to a certain extent the attributes desired to be attained, and it is the essential object of the invention to increase, or enhance, the value of these natural attributes, and this without breaking down the individual fibres or chemically changing or destroying their natural makeup; also to increase the affinity or fitness of the paper for receiving the bond by which the cloth or fabric is bonded to it.

Cylinder type paper is a paper possessing many of the attributes most to be desired in a paper adaptable for a combination due especially to the fact that it is made up of laminations or plies. These laminations, however, have a defect in the combination unless compensated for in that the laminations tend to separate, and it is, accordingly, a further object of the invention not only to enhance the natural attributes of the fibre in a combination employing a cylinder type paper component but also to bind together its laminations or plies and prevent their separation.

The treatment of the paper component in the combination is a treatment based upon saturation of the paper as distinguished from a mere surface treatment thereof. In order to obtain such'saturation paper of suitable weight, thickness, porosity, denseness and fibre furnish, is taken. There is preferably chosen what is known as unsized saturating paper for ease in treatment, and the usual specifications are a soft unsized lightly calendered rope paper with a paper makers basic weight of 200 lbs. per ream of 480 sheets 24 x 36. A cylinder type paper is also preferably used. This paper is saturated in a solution of gum, with or without glue. The solution must be of such consistency as to readily penetrate the paper, and of such character as to surround individual fibres, strengthening, supporting and binding them in one mass, but without chemically changing them or destroying their natural makeup. The solution must be, also, such that its residual component left in the paper will readily combine with glue or other substance which forms the bond between the paper and cloth or fabric bonded to it thereby increasing the aflinity or fitness of the paper for receiving such bond. A

number of gums and glues are available for this operation either singly or in combinations. The preferred formula is 25% gum arabic and 75% water. Satisfactory results are also obtained from solutions of bone and hide glue, or these combined with water soluble gums such as gum tragacanth, gum congo, gum karaya, gum kauri, gum sanadrac, and soy bean gum, or various combinations of these in solution with gum arabic, any or all of which have the faculty of binding together and strengthening cellulose and like fibres and has a strong aflinity for hide glue used as a bond for the cloth.

Where it is desirable to further support and strengthen the combination backing an additional sheet of cloth or other fabric may be glued to the back on the opposite side from that which affords the grain anchorage.

In the accompanying drawing Fig. l is a perspective view of a combination coated abrasive constructed according to the invention; and

Fig. 2 is a cross section on the line 2-2 of Fig. 1.

I represents the paper component of the combination treated as described. 2 and 3, respectively, represent cloth or fabric bonded to I, each by a bond 4. 5 is the abrasive coating which is applied to the face of 2 in the usual manner.

A further effective variation is the combination of alternate sheets of fabric and treated paper components to a greater number of plies than above described.

Combination backing having a paper component thus treated possesses all the advantages most to be desired in a coated abrasive which is subject to hard distortive usage as in an abrasive disk, and including strength, firmness, cohesion, resiliency, and ability to resist stretch and distortion. The combination will stand up, and not go to pieces, and this is due in no small part to the fact that the cloth is better bonded to the paper. than heretofore, the very matter which enhances the natural attributes of the paper increasing its aflinity orfitness for receiving the bond by which the cloth or fabric is bonded to it. When used in the abrasive disk the backing will wear remarkably well at or near its peripheral edge where most of the stress comes, and will not chip, so avoiding danger to the operator.

I claim:

1. A combination coated abrasive having a backing composed of paper to which is bonded a fabric, and an abrasive material bonded to the face of said fabric, said paper being an unsized paper saturated with a water soluble penetrating gum solution' whereby the natural attributes of the fibre structure of the paper and its affinity or fitness for receiving the bond by which the cloth or fabric is bonded to it are increased by the residual component of said solution without chemical change in said fibre structure.

' 2. A combination coated abrasive having a backing composed of paper to which is bonded a fabric, and an abrasive-material bonded to the face of said fabric, said paper being an unsized paper saturated with a water soluble penetrating combination gum and glue solution whereby the natural attributes of the fibre structure of the paper and its affinity or fitness for receiving the bond by which the cloth or fabric is bonded to it are increased by the residual component of said solution without chemical change in said fibre structure.

3. A combination coated abrasive having a backing composed of paper to which is bonded a fabric, and an abrasive material bonded to the face of said fabric, said paper being an unsized paper saturated with a water soluble penetrating solution containing gum arabic whereby the natural attributes of the fibre structure of the paper and its afiinity or fitness for receiving the bond by which the cloth or fabric is bonded to it are increased by the residual component of said solution without chemical change in said fibre structure.

JOHN F. A. DAVIS. 

